Blind rivet



Nov. 15, 1966 G. SIEBOL 3,235,121

BLIND RIVET Original Filed Dec. 28, 1961 2 Sheets-Sheet l INVENTOR.saeai 5/5504 Nov. 15, 1966 Original Filed Dec. 28, 1961 G- SIEBOL BLINDRIVET 2 Sheets-Sheet 2 16 54 INVENTOR. 640w: 5/5501.

United States Patent 3,285,121 BLIND RIVET George Siebol, 2877 ShadyGlen Lane, Orange, Calif. Continuation of application Ser. No. 162,791,Dec. 28, 1961. This application May 19, 1965, Ser. No. 459,523 8 Claims.(Cl. 85--72) This application is a continuation of my prior copendingapplication Serial No. 162,791, entitled, Blind Rivet, and filedDecember 28, 1961, which is now abandoned.

This invention relates to rivets, and more particularly to an improvedblind rivet, which is especially adapted for the riveting of work piececonfigurations, where access may conveniently be had from one side only.The side of the work from which the rivet is applied is often referredto as the top side and will be so referred to herein. The other side ofthe work is generally called the blind side.

Most blind rivets presently in use include two basic parts, viz. atubular member and a setting pin telescopically received in the tubularmember. The tubular member is usually called a sleeve and embodies ashank and a radially enlarged head integral with one end of the shankand which is seated against the top side of the work when the rivet isinstalled.

Blind rivets may be generally classified into two classes, one in whichthe setting pin is driven into the tubular member from the top side andother in which the setting pin is pulled outwardly fromthe top side toset the rivet. The fasteners discussed herein are of the latter class,i.e., the pull type. The setting pin of a pulltype blind rivet isprovided with a tail or pulling portion at one end adapted to moverelatively freely through the sleeve and projecting at the top side, anda head portion at the blind end having a diameter greater than theinternal diameter of the sleeve. Prior to use, the sleeve and pin areassembled with the pin in the sleeve with its pulling portion projectingfrom the headed end or top side and its head portion located at or nearthe shank or blind end of the sleeve.

In use, the rivet assembly is inserted from the top side, head portionof the pin first into aligned apertures in the work pieces to beriveted. When properly oriented, the head of the sleeve abuts the topside of the work pieces and the shank of the sleeve, along with the headof the pin, project exteriorly on the blind side of the work pieces. Toset the rivet, a pulling force is applied to the tail of the pin and areactive or restraining force is applied to the head of the sleeve. Thisserves to draw the head of the pin into the sleeve shank which resultsin the shank being radially expanded or upset on the blind side to lockor clinch the work pieces together.

It is also desirable in setting a blind rivet to expand the sleevewithin apertures in the work pieces into pressure engagement with thewalls thereof, thus improving the shear strength of the resultingconnection.

Frequently, the work pieces which are to be riveted together areinitially separated from each other so that they must be pressed orclinched together simultaneously with riveting. To achieve this endwithout having to clamp the pieces together by some independent means itis desirable that the projecting portion of the shank on the blind sidemust be expanded sufilciently to clinch the work pieces together beforethe shank portion within the apertures is expanded against the walls ofthe apertures. If this is not done, i.e., if the expansion of the shankportion within the apertures takes place before or simultaneously withthe so-called free air expansion of the shank, effective clinching doesnot take place. That is, premature expansion of the sleeve within thework piece apertures tends to lock them in their separated positions andprevent clinching. Failure properly to clinch the work pieces, precludesthe rivet from developing either the desired shear or tensile strength.Therefore, it will be appreciated that a satisfactory rivet of thepresent type must operate to first clinch the work pieces together and,thereafter, be upset to secure them in that position.

In prior devices, after the pin has been moved into the tubular memberthe desired extent, various means have been employed to stop further pinmovement and lock the pin and sleeve together. In some cases, thepulling force is merely discontinued when the desired pin movement hastaken place, and friction alone between the contacting surfaces of thepin and sleeve is relied upon for retention of the pin and formaintenance of tensile strength. Other prior rivets embody a sleeve witha reduced diameter, projecting head portion or crown which is swagedradially inwardly against the pin as setting of the rivet takes place.In this latter case, the gripping action of the swaged metal supplementsthe frictional contact between the pin and the sleeve to retain theparts in assembly and to maintain tensile strength.

In order to leave a final riveted connection which is relatively flushwith the exposed top side work pieces without having to trim the pin ina separate operation, it is conventional in the art to provide the pinwith a weakened section termed a breakneck groove. The pin is arrangedto fracture at the breakneck groove when the pulling force thereonreaches a predetermined maximum, whereupon the protruding pullingportion of the pin separates from the remaining portion disposed withinthe sleeve.

In rivets of the above described type, it has been found that thetensile strength developed is frequently inadequate. A contributingfactor of this lack of adequate tensile strength is that the pin andsleeve take on complementary tapered configurations at their juncturesurface as the former is drawn into the latter. The resulting taper isso directed that the diameter of the juncture surface increases towardthe blind end, thus facilitating retrograde movement of the pin out ofthe sleeve. Further, the resilient metal in the pin is strained somewhatduring setting, so that when the pulling force is rapidly released byfracturing of the pin at the breakneck groove, the pin tends to springback slightly. As a consequence, clinching force on the work pieces isrelaxed somewhat and the joint is apt to become loose. Moreover, thetensile strength of the rivet is greatly reduced. This latter resultfollows from the fact that with the tapered configurations of thecooperating parts, the gripping or retention force of the sleeve on thepin diminishes very rapidly as the pin backs out of the sleeve.

A problem is also encountered in the situation where swaging of metalradially inwardly against the pin is depended upon to give the necessarytensile strength. The problem here is that the pin is pinchedprematurely while still being drawn into the sleeve. The significantlyincreases the pulling force required to set the rivet and necessitatesthe use of a more powerful pulling tool. Moreover, it often results infracturing of the pin at the breakneck groove before the rivet is fullyset.

To overcome these problems of inadequate tensile strength encountered inprior rivets, various expedients have been tried. One such expedientwhich has been partially successful in solving the immediate problem isto provide a locking collar around the pin adjacent the head of thesleeve adapted to be swaged inwardly into a corresponding groove in thepin after it has been pulled the desired distance into the sleeve.Setting of such a rivet is achieved by means of a pulling tool whichinitially applies the reactive force to the head of the sleeve and then,after the pin is finally positioned, to the locking collar. Thus, thelocking collar is not swaged inwardly until the requisite pin movementhas already taken place. Although this solution has been somewhatsuccessful, as suggested above, it greatly increases the complexity and,hence, the initial cost of the pulling tool. Besides the cost of thetool, the labor costs involved are also substantially increased byvirtue of adjustment of the tool having to be made for each new totalthickness of Work pieces, or grip length, as it is termed in the art.

In view of the foregoing discussion, it is a primary object of thisinvention to provide a low cost pull type blind rivet which is adaptedto ailord a greatly improved riveted connection, as compared to priorblind rivets, particularly with respect to tensile strength.

Another object is to provide a blind rivet of the type described, whichfunctions to establish and maintain high clinching forces on the workpieces riveted.

A further object is to provide a pull type blind rivet embodying asleeve and an associated setting pin having a breakneck groove at whichthe pin is adapted to fracture when tension reaches a predeterminedmaximum level, the two parts cooperating in such a manner thatfracturing of the pin of the breakneck groove has virtually no tendencyto cause separation of the pin and the sleeve.

It is a further object of this invention to provide a pull type blindrivet characterized in that it is capable of affording a high strengthriveted connection in spite of tolerance variations both in the size ofthe apertures in the work pieces and in the total thickness thereof.

Another object is to provide a rivet which, when fully set, isessentially flush with the exposed top side of the riveted work pieces.

Still another object is to provide a rivet for accomplishing all of theforegoing objects, yet one which is economical both from the standpointof initial cost and from the standpoint of labor costs incurred insetting it. It is another object to provide a pull type blind rivetwhich is adapted to be set by an extremely simple and, hence,inexpensive pulling tool.

These and other objects and advantages of the invention willbe betterunderstood by referring to the following detailed description taken inconjunction with the accompanying drawings in which:

FIGURE 1 is a perspective view of a rivet constructed in accordance withthe invention and illustrating the associated sleeve and pin, asassembled for use prior to setting;

FIGURE 2 is a view of the rivet of FIGURE 1, showing the sleeve inlongitudinal section and the pin in elevation; FIGURE 3 is a partialsection on an enlarged scale of the headed end of the sleeve;

FIGURE 4 is a view, partially in longitudinal section and partially inelevation, showing the rivet of FIGURE 1 positioned in a pair of spacedapart work pieces to be riveted together and attached to a setting toolat the beginning of the setting operation;

FIGURE 5 is a view similar to FIGURE 4, illustrating the rivet parts inrelation to the Work pieces at the completion of the first or clinchingphase of the setting operation;

FIGURE 6 is an enlarged view similar to FIGURES 4 and 5, illustratingthe cooperating parts in relation to the work pieces after anintermediate phase of the setting operation; and

FIGURE 7 is an enlarged view similar to FIGURES 4, 5, and 6,illustrating the rivet as finally set in the work pieces.

Referring to the drawings and in particular to FIG- URE 1, the rivet ofthe invention is indicated generally by the reference numeral 10. In theposition shown in FIGURE 1, the blind side of the rivet is on theleftand the top side to the right. As may be seen, the rivet 10 includestwo basic parts. One of these is a sleeve 12 and the other a setting pin14. The construction of the sleeve and pin, as well as the manner inwhich they cooperate to provide a secure joint, are described in detailbelow. Satisfactory results may be achieved when the two basic rivetparts are formed of a variety of different metals. However, aluminumalloys have been found to yield particularly advantageous results.

The sleeve 12 includes a shank 16 with a radially enlarged head 18 atone end. The shank is tubular in shape with a concentric axial bore 20.

In the illustrative embodiment of FIGURE 1, the sleeve head 18 is of theso-called countersunk type, however, it will be understood that othertypes may be used effectively. Being of the countersunk type, the head18 includes a radially enlarged, frusto-conical flange 22.

As shown in FIGURES 2 and 3, the head 18 has a locking crown 24projecting axially from the top side of the flange 22 and oppositely ofthe shank 16. A reduced diameter portion 26 of the bore 20 extendsthrough both the flange 22 and the locking crown 24. As will beexplained more fully below, the bore portion 26 in the head 18 is of asmaller diameter than the main portion of the bore 20 to provide anannular stop shoulder 28 (FIGURE 3) at their junction facing toward theblind end of the sleeve.

As may be seen in FIGURES 2 and 3, the flange 22 of the head 18 has anundercut annular groove 30 immediately adjacent to and spaced radiallyoutwardly of the locking crown 24. The groove walls are generallyparallel and slope inwardly from top to bottom toward the axis of thesleeve 12, the inner groove wall 32 defining the base periphery of thelocking crown 24. For purposes of description, the projecting portion ofthe crown 24 is considered to be that portion which projects outwardlybeyond the plane defined by the top side 1 of the flange 22 andindicated by the reference line 33 in FIGURE 3. By virtue of the slopeof the groove wall 32, the crown 24 takes on a generally frusto-conicalexternal shape. The cylindrical bore through the crown 24 gives itminimum and maximum thickness wall sections at its inner and outer ends,respectively. I Turning now to the cooperating setting pin 14, itembodies, in series, a pulling section 34, an expanding section 36, anda blind head 38. The diameters of the respective sections aresuccessively larger, with that of the pulling section 34 being thesmallest. At the junction of the pulling and expanding sections 34 and36, respectively, a tapered annular shoulder 40 is formed. Similarly, asecond tapered annular shoulder 42 is formed at the junction of theexpanding section 36 and blind head 38.

In order to achieve positive locking of the sleeve 12 and pin 14 aftersetting, an annular locking groove 44 is provided in the pin and isadapted to receive the locking crown 24, as the latter is buckled orcollapsed inwardly in the rivet setting operation. As illustrated inFIGURE 2, the groove 44 is located in the pulling section 34 immediatelyadjacent the junction of the pulling section and the expanding section36. To the right of the locking groove 44 in FIGURE 2, the pullingsection 34 of the pin has a breakneck groove 46. As discussed above,this last mentioned groove is the weakest section of the pin. Tofacilitate gripping of the pulling section 34 when setting the rivet, itis preferably formed with a plurality of relatively shallow annulargrooves 48 extending from a point adjacent its outer end to a pointadjacent the head 18 of the sleeve 12, when the rivet is assembled foruse.

Relating the dimensions of the pin 14 to those of the sleeve 12, thediameter of the pulling section 34 is slightly less than the minimuminternal diameter of the sleeve' ,12.- With these relative dimensions,the pulling section 34 is free to move through the sleeve 12. In someinstances, it may be desired to provide an annular ridge on the pullingsection, as in the present case at 50, adapted to be received in aninterference or press fit in the sleeve. The purpose of the ridge 50 isto maintain the two parts in the assembled condition of FIGURES 1 and 2prior to use.

The diameter of the expanding section 36 is greater than the diameter ofthe bore 20 of the shank 16 in which it is to be received. The stilllarger diameter blind head 38 has a diameter preferably about equal to,but no greater than the outside diameter of the shank 16. This is toinsure that the assembled rivet may be inserted in aligned apertures inthe work pieces to be riveted from the top side thereof, it beingassumed that the apertures are just slightly larger in diameter than theshank 16.

The relative lengths of the various sections of the pin and the sleevedepend primarily on the combined thicknesses of the work pieces to beriveted, as has been suggested above. In general, the length of thesleeve 12 is preferably at least equal to the length of the pin 14 fromthe breakneck groove 46 to the terminal end of the blind head 38. Thisis desired in order to establish frictional contact between the surfacesof the two parts over as great a length as possible. Further, the sleeve12 is sufilciently long, so that when it is inserted in a plurality ofwork pieces to be riveted with its head flush on the top side, the blindend of the shank 16 projects at least a small distance on the blind sideof the work.

In order to enhance the improved results afforded by the present rivet,the relative hardnesses of the several sections of the pin arepreferably equal, except for the particular areas formed with thelocking groove 44, the breakneck groove 46, and the pull grooves 48.Such relative hardnesses are established by the particular manner inwhich the pin 14 is formed. In such forming, a length of wire is firstcold formed in a header to give a pin having the general shape of thefinal product, but for the grooves 44, 46, and 48. After cold heading,the hardnesses of the respective sections diifer in accordance with theextent to which they have been extruded or cold worked. As is well knownin the art, the greater the cold working, the greater the unit hardness.Accordingly, in the next step of the process, the partially formed pinis annealed to equalize the hardnesses of the various sections.

As a final step in shaping the pin 14, the grooves 44, 46, and 48 arerolled in at their respective positions described above. Forming of thegrooves results in the metal of the pin at these grooves being coldworked and thereby hardened. In this regard, it is important to notethat since the locking groove is formed immediately adjacent theshoulder 40, the leading edge portion 52 of that shoulder is workhardened. Thus, the unit hardness of the annular leading edge portion 52of the shoulder 40 in the finally shaped pin is greater than that of theexpanding and blind head sections 36 and 38, respectively.

With the foregoing discussion of the construction of the sleeve 12 andpin 14 of the rivet in mind, it is believed that the cooperativeassociation of these members to achieve riveting can be best understoodby following through a description of the setting operation. To assemblethe rivet for packing and shipment, the pin 14 is inserted, pulling end34 first, into the shank end of the sleeve 12. The position of the partsafter assembly is illustrated in FIGURES 1 and 2, where it will be seenthat the pulling section 34 extends through the sleeve 12, and agripping portion thereof projects from the head 18, whereas theexpanding section 36 and the blind head 38 project from the shank 16.

The work to be riveted is assumed, in the present case, to comprise apair of fiat work pieces 54 provided with aligned apertures 58 andintially separated a small distance, as shown in FIGURE 4. Since thehead 18 of the sleeve 12 is of the countersunk type, the exposed topside 54a of the work is provided with a mating countersink 60 adapted toreceive the head 18. The other exposed side 54b of the work is the blindside. In normal operating circumstances, access may be had to the topside 54a only.

In positioning the rivet for setting, it is inserted from the top side54a, the blind head 38 of the pin 14 first, through the alignedapertures 58; When finally positioned, the sleeve head 18 is pressedfirmly against the top side 54a and the shank 16, as well as theprojecting portions of the pin, project on the blind side 5412. In orderto achieve maximum strength, the relative diameters of the apertures 58and shank 16 are such that the shank may be quickly and easily inserted,but with a minimum of free clearance.

To commence the setting operation, pulling force is applied to thepulling section 34 of the pin 14 and a re"- active force is applied tothe locking crown 24. This causes the expanding section 36 to be drawninto the shank 16 to radially expand or upset the same. This expansioncauses an expansion wave on the exterior of the shank 16 to move axiallyfrom the blind end toward the sleeve head. As the expansion Wave reachesthe blind side of the work piece, as illustrated in FIGURE 5, theindividual work pieces 54 are moved or clinched together. Thus, thisphase of the setting operation may be considered as the clinching phase.

As illustrated in FIGURES 2 and 4, the shank 16 is preferably providedwith a counterbore 62 at its blind or inner end. The function of thecountenbore 62 is to insure that when the tapered shoulders 40 and 42 onthe pin enter the shank 16, splitting of the shank does not take place.The shank 16 is less likely to split inwardly of its blind end than thatat the end.

Once the work pieces are fully clinched, as in FIGURE 5, the expandingsection 36 is drawn into and caused to expand the portion of the shank16 within the apertures 58 in the work pieces. Increased resistance toexpansion is encountered as the'sleeve is expanded into pressureengagement with the walls of the apertures 58. Because of this increasedresistance, the expanding section 36 is drawn somewhat decreasing itsdiarneter as necessary to permit its continued movement. FIGURE 6illustrates the rivet parts near the completion of such expansion of theconfined portion or" the shank 16 and of the resulting wiredrawing ofthe expanding section 36 of the pin 14. Tolerance variations,particularly in the diameter of the apertures 58 and also in the rivetparts, are accommodated in this manner. That is, by making the expandingsection 36 of a diameter larger than that actually required tosufficiently expand the shank 16 into pressure contact with the walls ofthe apertures 58 and then allowing the excess to be taken up bywiredrawing, tolerance variations are accommodated.

During this last mentioned phase of expansion of the shank 16 and thewiredrawing of the expanding section 36 of the pin 14, the blind head 38enters and brings about further free air expansion of the inwardlyprojecting end of the shank. Since the resistance to expansion of theprojecting, and hence unconfined, end portion of the shank 16 isrelatively small, it expands, and the blind head 38 retains its originalshape.

Movement of the pin 14 relative to the sleeve 12 continues under theinfluence of the pulling and reactive forces, until the pin reaches therelative position shown in FIGURE 6. At this point, the annular workhardened edge 52 of the shoulder 40 abuts the stop shoulder 28 in thesleeve 12. Further movement of the pin 14 into the sleeve 12 at thispoint 'meets sharply increased resistance on two separate accounts. Tobegin with, the reduced diameter portion 26 of the bore in the head 18would necessitate the sleeve expanding or the pin drawing a relativelygreater amount than during prior movement. Second-1y, any radialexpansion of the sleeve 12 in the area of the bore portion 26 is subjectto a relatively high degree resistance due to the increased radialthickness of the head 18, as compared to that of the shank 16.Therefore, since wiredrawing of the pin 14 to the extent required topermit it to move into the bore portion 26 is strongly resisted by theannular work hardened edge portion 52 of the shoulder 40, pin movementstops. It is to be noted that when relative movement ceases, the lockinggroove 44 of the pin 14 is disposed immediately adjacent the lockingcrown 24.

When pin movement stops, tension in the pin 14 and compression of thelocking crown 24 both increase due to a corresponding increase in thepulling and reactive forces. Referring now to FIGURE 7, it will be seenthat the locking crown 24 is so constructed and arranged that when theforces reach a predetermined level, the crown 24 is buckled inwardlyinto the locking groove 44 of the pin 14. After the groove 44 is filled,the excess material of the crown 24 is flattened into the annular groove30. It will be appreciated that by suitably forming the cooperatingparts, the ratio of the force required to buckle the locking crown 24 tothe force required to draw the pin 14 into the shank 16 can beestablished as desired. In the present case, the ratio is approximately2 to 1, thereby insuring that the pin moves the requisite distance intothe sleeve before such buckling takes place.

An important feature of the present rivet is that just prior to theabutment of the work hardened edge 52 of the shoulder 40 with theshoulder 28, the head 38 of the pin further expands the projecting tailportion of the shank 16 into contact with the blind side 54b of thework. In accomplishing this, the shoulder is deformed somewhat, as maybe seen in FIGURE 6, but is not substantially drawn into the portion ofthe shank 16 confined within the apertures 58. It will be appreciatedthat in order to eifect such expansion without wiredrawing the pin head38, the length of the expanding section 36 is established in accordancewith the total thickness of the work pieces to be riveted.

Furthermore, the grip range of. the rivet is controlled by the axiallength of the tapered shoulder 42. To elaborate, under minimum gripconditions, the leading edge of the tapered shoulder 42 would be drawnup so as to just :force the projecting and radially expanded tailportion of the shank 16 into pressure contact with the blind side 54b ofthe work around the aperture 58. On the other hand, under maximum gripconditions, the shoulder is deformed somewhat with its leading edgeactually slightly entering the aperture 58 and its terminal edge beingpulled up relatively close to the plane of the blind side 54b of thework.

The advantage of this additional free air expansion accomplished by theblind head 38 is that it significantly increases the tensile strength ofthe rivet. As is well known, the greater the area of contact, the lessthe unit pressure. Accordingly, the greater the area of the shank 16which is forced into contact with the blind side 54b of the work, theless tendency there is for the rivet to pull back out of the work underthe influence of tensile forces tending to separate the individual workpieces 54.

In further regard to strength of the riveted connection, it is to benoted that by virtue of the locking crown 24 being buckled into thecooperating groove 44 in the pin 14, positive locking of the two rivetparts in assembly with one another is effected. The pin 14 is precludedfrom backing out of the sleeve 12 by this locking relationship,supplemented by the frictional contact between the pin and sleeve.Conversely, the pin 14 is precluded from moving on through the sleeve bythe same locking relationship between the buckled crown and pin and bythe frictional contact and, in addition, against wiredrawing downsufficiently in size to permit it to move into the portion of the shank16 confined within the apertures 58 of the work.

Continuing the description of the setting operation, once the lockingcrown 24 is buckled and flattened to the condition shown in FIGURE 7,tension on the pin 14 further increases as a consequence of the sharplyincreased resistance to its movement. By suitably forming the pin 14,the breakneck groove 46 can be made to fracture when the forces exceedthose required to set the pin by a predetermined amount. Preferably, theforces required to fracture the pin 14 are just slightly greater thanthose required to finally buckle the locking crown 24. At least a slightdifference is necessary in order to insure that the crown 24 is fullybuckled and flattened in the manner previously described before the pinfractures. On the other hand, it is desired to minimize this differencein order that the rivet is not subjected to excessive force after it isfinally set and also to minimize the power requirements of the tool.

When the tension in the pin 14 reaches the above dis cussedpredetermined level, the pin fractures at the breakneck groove 46, asillustrated in FIGURE 7. This results in the pulling section 34separating from the remainder of the pin 14 disposed within the sleeve12 in the plane of the head 18. Preferably, the volume 'of the initiallyprojecting portion of the crown, i.e., the portion to the right of thereference line 33 in FIGURE 3, is made approximately equal to thecombined voids of the locking groove 44 and annular groove 30. With thisvoid-volume relationship, the end face of the crown 24 is disposedgenerally flush with the head 18 of the sleeve after it is buckled andflattened. Moreover, since the head 18 is here of the countersunk type,the resulting rivet is generally flush with the exposed top side 54a ofthe work.

It will be recalled from the introductory discussion that when the pinof certain prior rivets fractures, the springback forces tend toseparate the pin from the sleeve. An important feature of the presentrivet is that once the locking crown 24 is buckled, the pin 14 iseffectively gripped at its locking groove 44 and the strain occurring inthe rivet thereafter is limited for all practical purposes to thesection of the pin between the locking groove 44 and the pulling sectionwhere the pulling force is applied. Accordingly, when the pin 14fractures, any springback takes place essentially only over the shortlength of the pin between the breakneck groove 46 and the locking groove44. Moreover, locking of the sleeve 12 and pin 14 in assembly with oneanother takes place between the locking groove and the opposite end ofthe pin. Thus, for the first of these reasons, there is practically nospringback in the first place. Moreover, any which does occur hasvirtually no effect on the gripping relationship between the two parts.

A tool 66 for setting the rivet in the manner set forth above isillustrated in FIGURE 5. The primary operational requirement of the tool66 is that a pulling force be applied to the pulling section 34 and thata substantially equal and opposite reactive force be constantly appliedin an axial direction to the locking crown 24.

-. As shown in FIGURE 5, the tool 66 includes a housing 68 having anaxial bore 70. The forward end of the housing is necked down andexternallythreaded, as at 72. Projecting axially from the forward endof'the housing 68 is an annular boss or thrust member 74 which is formedwith a central bore-76 coaxial with the bore 7 0. The bore 76 is of adiameter such that the pulling section 34 of the pin 14 may be receivedfreely therein and such that the forward end of the thrust member 74 mayabut the locking crown 24 in setting the rivet.

Concentrically mounted on the thrust member 74 is an annular centeringsleeve 78. The function of the centering sleeve 78 is to slip around thelocking crown 24 when the tool 66 is being positioned for use to centerthe thrust member 74 with respect to the locking crown and insure thatthe pulling and reactive forces are applied in axial directions. Toretain the centering sleeve 78 in assembly with the housing 68, it isformed with a radially projecting 9 flange 80 at its rearward end. Thisflange 80 is adapted to abut a cooperating flange 82 on a retainersleeve 84 screw threaded on the aforementioned externally threadedportion 72 of the housing 68.

When so mounted, the centering sleeve 78 is free for limitedlongitudinal movement with respect to the integral thrust member 74 andhousing 68. A relatively light leaf spring 86 is disposed between thehousing 68 and the centering sleeve 78 and serves to urge the latter toits extreme forward position, wherein it projects forwardly at theforward end wall of the thrust member 74. As shown, the sleeve 78 hassufficient freedom for longitudinal movement to enable it to moveinwardly to a rearward position, wherein it is flush with the forwardend wall of the thrust member 74. This insures that the reactive forceis constantly applied to the locking crown 24 as the latter is buckledinwardly.

A collett-like chuck 90 is provided for gripping the pin 14 and pullingit relative to the housing 68. The chuck 90 includes gripping jaws 92and a concentrically mounted closing and pulling member 94. The chuck 90is slidably mounted in the bore 70 of the housing 68 and adapted formovement from the initial operating position, illustrated in FIGURE 5,toward the right in that figure.

The forward ends of the gripping jaws 92, as well as the engagingsurface of the closing and pulling member 94, are frusto-conical inshape, so that when an axial force is applied to the member 94 to moveit outwardly or to the right in FIGURE 5, the jaws 92 are clampedinwardly toward one another. It will readily be appreciated that whensuch an actuating force is applied, the jaws 92 clamp the pullingsection 34 of the pin 14 and pull the pin in the desired manner.Preferably, the inner walls of the jaws 92 are grooved to mate with theannular grooves 48 on the pulling section of the pin and insure positivegripping. A suitable actuating mechanism (not shown) is provided for sourging the member 94 to the right in FIGURE 5. Such mechanism alsooperates in a known manner to return the member 94 to its initialposition to release the jaws 92 for insertion of a new rivet.

In use, assuming the rivet to have been positioned in the work pieces,the setting tool 66 is simply applied over the projecting pullingsection 34 of the pin 14 to the position shown in FIGURE 5. The jaws 92are initially separated a sufiicient amount to receive the pullingsection. When the thrust member 74 is positioned in abutment with thelocking crown 24, the tool 66 is actuated to move the member 94 to theright with respect to the housing in FIGURE 5. As described above, thisserves to clamp the jaws 92 on the pulling section 34 and pull the pinrelative to the housing 68 and exert an opposite force on the lockingcrown 24. Setting of the rivet takes place in the manner described indetail above with the operation being terminated when the pin fracturesat its breakneck groove 46, separating the pulling section 34 from theremaining portions of the rivet. When this separation takes place, thepulling assembly 90 preferably springs back to its original position,illustrated in FIGURE 5, whereupon the jaws 92 separate and the brokenoff portion of the pin 14 is either ejected from the tool 66 or releasedand drops free of the housing.

From the above description of the setting tool 66 it will be appreciatedthat it is extremely simple in construction and, hence, inexpensive tomanufacture. The use of such a tool to yield the highly effectiveresults obtained in the present case is made possible by the specifiedrivet parts and the particular manner in which they cooperate in thesetting operation. As explained, the tool need only apply pulling forceto the pin 14 and reactive force to the locking crown 24 on the sleeve12. The rivet parts are arranged so that when, under the influence ofthese forces,

the pin 14 is moved the requisite distance in the sleeve 12,

movement is automatically stopped and the resistance to pulling risessharply. This sharp rise in resistance causes the locking crown 24 to bebuckled inwardly into locking relationship with the pin. Following thislocking of the parts in assembly with one another, the pulling and reactive forces increase the tension in the pin 14. When this tensionreaches a predetermined level, the pin 14 fractures at the breakneckgroove 46 to terminate the setting operation. Thus, the various phasesof the setting operation takes place in desired sequence by virtue ofthe cooperative relationship of the rivet parts.

Although one embodiment of the invention has been shown and described inconsiderable detail, it will be understood that various changes in thedetails of construction and arrangement may be made without departingfrom the spirit and scope of the invention as defined in the appendedclaims.

I claim:

1. A blind rivet adapted to be inserted from the top side and set in thealigned apertures in a plurality of work pieces, comprising:

a tubular sleeve including a shank with a radially enlarged head at oneend and an axial passageway extending therethrough from end to end, saidsleeve being adapted to be inserted into the aligned apertures in thework pieces with said head abutting the top side of the same and withthe shank projecting from the opposite blind side of the work pieces;

a pin including, in series, a pulling section initially disposed in saidpassageway with a gripping end projecting from the headed end of saidsleeve, an expanding section of a cross-section greater than that ofsaid passageway and initially projecting from the shank end of thesleeve, and a blind head outward of, and larger in diameter than saidexpanding section so as to provide an annular tapered second shoulder atthe juncture of the blind head and expanding section, said expandingsection being adapted upon an axial pulling force being applied to saidpulling section and a reactive force opposite to said radially enlargedhead to be drawn into said passageway to expand the projecting portionof said shank and, thereafter, the portion thereof disposed within thealigned apertures in said work pieces, said blind head being adaptedupon the continued application of such forces to be drawn into theprojecting portion of said shank to further expand the same;

first shoulder means on the exterior of said pin axially spaced fromsaid second shoulder toward said pulling section, which is of a unithardness greater than that of at least said expanding section and saidsecond shoulder, and stop shoulder on the interior of said sleeveadjacent said radially enlarged head engageable to stop pin movement,said expanding section being adapted to be pulled into the blind end ofsaid shank to expand the same and to wiredraw down in diameter and,thereafter, said blind head being adapted to be pulled into said shankto further expand the same with said second shoulder being drawn upadjacent the blind side of the work pieces and deformed to expand theaxially aligned portion of the shank into engagement with the blind sideof the work pieces, the extent to which said expanding section and blindhead are and said sec-ond shoulder is deformed being limited by theleading edge of said first shoulder abutting said stop shoulder in saidsleeve; and

means adjacent said radially enlarged head for locking said pin againstmovement relative to said sleeve, and means located on said pin adjacentsaid first shoulder and between said first shoulder and said pullingsection for receiving said locking means.

2. A blind rivet adapted to be inserted from the top side and set in thealigned apertures in a plurality of work pieces, comprising:

a tubular sleeve including a shank with a radially enlarged head at oneend and an axial passageway expulled into said shank tendingtherethrough from end to end, said sleeve being adapted to be insertedinto the aligned apertures in the work pieces with said head abuttingthe top side of the same and with the shank projecting same and towiredraw down in diameter and, therethe portion thereof disposed'withinthe aligned apertures in said work pieces, said blind head being adaptedupon the continued application of such forces to be drawn into theprojecting portion of said shank to from the opposite blind side of thework pieces; further expand the same;

a pin with three successively larger sections including, and firstshoulder means on the exterior of said pin in series, a pulling sectioninitially disposed in said axially spaced from said second shouldertoward said passageway with a gripping end projecting from the pullingsection, which is of a unit hardness greater headed end of said sleeve,an expanding section of a than that of at least said expanding sectionand said cross-section greater than that of said passageway secondshoulder, and a stop shoulder on the interior and initially projectingfrom the shank end of said of said sleeve adjacent its head engageableto stop pin sleeve, and a blind head, there being a first taperedmovement; said expanding section being adapted to shoulder at thejunction of said pulling and expandbe pulled into the blind end of saidshank to expand ing sections and a second shoulder at the junction ofthe same and to wiredraw down in diameter and, said expanding sectionand said blind head, the unit 15 thereafter, said blind head beingadapted to be pulled hardness of the leading edge of said first shoulderinto said shank to further expand the same with second being greaterthan that of the remainder of the pin shoulder being drawn up adjacentthe blind side of toward and including said blind head so as to resistthe work pieces and deformed to expand the-axially wiredrawing, saidexpanding section being adapted aligned portion of the shank intoengagement with to be drawn into said passageway to expand the protheblind side of the work pieces, the extent to which jecting portion ofsaid shank and, thereafter, the said expanding section and blind headare pulled into portion thereof disposed within the aligned aperturessaid shank and said second shoulder is deformed in said work pieces,said blind head being adapted to being limited by the leading edge ofsaid first shoulder be drawn into the projecting portion of the shank toabutting said stop shoulder in said sleeve, and means further expand thesame; located on said pin adjacent said first shouder and stop shouldermeans on the interior of said sleeve adjabetween said first shoulder andsaid pulling section cent said radially enlarged head engageable withthe for receiving said locking crown whereupon the conleading edge ofsaid first shoulder to stop pin movetinued application of such forcesresults in said ment; said expanding section being adapted to be crownbeing buckled into locking relationship with pulled into the blind endof said shank to expand the said pin.

4. A blind rivet adapted to be inserted from the top side and set in thealigned apertures in a plurality of work pieces, comprising:

a tubular sleeve including a shank and a radially enafter, said blindhead being adapted to be pulled into said shank to further expand thesame with said second shoulder being drawn up adjacent-the blind side ofthe work pieces and deformed to expand the axially aligned portion ofthe shank into engagement with the blind side of the work pieces, theextent to which said expanding section and blind head are pulled intosaid shank and said second shoulder is deformed being limited by theleading edge of said first shoulder abutting said stop shoulder in saidlarged head on one end provided with a locking crown projecting axiallyin a direction opposite said shank, said sleeve having an axialpassageway extending therethrough from end to end comprised of a firstbore of given diameter substantially coextensive with said shank and anadjoining second bore of reduced diameter substantially coextensive withsaid sleeve;

and means positioned adjacent the top side of said radially enlargedhead and engageable with said pin following such stopping of pinmovement for locking said pin against movement relative to said sleeve,and

head, there being an annular stop shoulder at the junction of said firstand second bores;

a pin having a plurality of successively larger diameter sectionsincluding a pulling section initially disposed partly within saidsleeve, an expanding section of a means located on said pin adjacentsaid first shoulder and between said first shoulder and said pullingsection for receiving said locking means.

diameter greater than that of said first bore, and a blind head, therebeing a shoulder intermediate said pulling and expanding sections, theleading edge of 3. A blind rivet adapted to be inserted from the topside and set in the aligned apertures in a plurality of work pieces,comprising:

a tubular sleeve including a shank with a radially en which has agreater unit hardness than that of the remainder of said pin toward andincluding said blind head, and a tapered annular shoulder intermediatesaid expanding section and blind head, said expandlarged head on one endprovided with a locking crown projecting axially in a direction oppositesaid shank, there being an axial passageway through said sleeve from endto end, said sleeve being adapted to be inserted into the alignedapertures in the work pieces with said head abutting the top side of thesame and with the shank projecting from the opposite blind side of thework pieces;

a pin including, in series, a pulling section initially disposed in saidpassageway with a gripping end projecting from the headed end of saidsleeve, an expanding section of a cross-section greater than that ofsaid passageway and initially projecting from the shank end of thesleeve, and a blind head outward of, and larger in cross-section thansaid expanding section so as to provide an annular second shoulder atthe juncture of the blind head and expanding section, said expandingsection being adapted upon an axial pulling force being applied to saidpulling secing section being adapted upon an axial pulling force beingapplied to said pulling section and a substan-' tially equal andopposite reactive force to said locking crown to be pulled into theblind end of said shank to expand the same and to wiredraw down indiameter in accordance with the resistance to expansion of the shankand, thereafter, said blind head being adapted to be pulled into saidshank to expand further the same with said tapered annular shoulderbeing deformed to urge the axially aligned portion of the shank intoengagement with the blind side of the work pieces, the extent to whichsaid expanding section and blind head are pulled into said shank andsaid tapered annular shoulder is deformed being 5011 and a Team? form ppto Said locking 5. The subject matter of claim 4 further characterizedcrown to be drawn into Said passageway to expand in that the magnitudeof the forces required to so buckle the P ot P t of Said Shankthereafter, Said crown is subStantially greater than that required topull said expanding section and said blind head into said shank;

and in that the pin is provided with a breakneck groove adjacent saidfirst shoulder, but toward the top side end of said pulling section, andarranged to be positioned flush with the top side of said head upon suchengagement of said leading edge with said stop shoulder, the crosssection of said pin being minimum at said breakneck groove whereby theapplication of such forces of a magnitude greater than ly equal to thecombined voids of the locking groove in said pin and the recessed groovein said sleeve head.

8. A blind rivet adapted to be inserted from the top side and set in thealigned apertures in a plurality of work pieces, comprising:

a tubular sleeve including a shank with a radically enlarged head on oneend provided with an integral locking crown projecting axially in adirection opposite said shank, there being a recessed annular neckgroove.

groove in the exterior end of said head immediately that required to sobuckle Sdld crown results in the ad acent to and spaced radiallyoutwardly of said fracturing of said pin at said breakneck groove.locking crown which is axially convergingly directed 6. A blind rivetadapted to be inserted from the top toward said shank, thereby providingadjacent, subside and set in the aligned apertures in a plurality ofstantially parallel conical surfaces in the groove and work pieces,comprising: 15 locking crown formed thereby, said tubular sleeve atubular sleeve h av1ng a shank with a head on one having an axialpassageway extending therethrough end, saidhead mclud ng a radiallyenlarged flange from end to end comprised of a first bore of given andlocking crown lntegral withf and projecting diameter substantiallycoextensive with said shank axially from said flange oppositely rom saidshan and an adjoining second bore of reduced diameter there being arecessed annular groove in said flange substantially coextensive withsaid head, there being innrifidiatgly gdi'acint to and splaclid rad allyoutan anrflulari isitop shioulder said sleeve at the juncwar y 0 S31 0clng crown W 1C 18 axta y C011- t ono sai rst an secon ores; verginglydirected toward said shank, whereby Said and a pin initially disposedwithin said sleeve and inlocking crown formed thereby has the gen rabcluding, in series, a pulling section of a diameter at f a truncated che ap portlon 0f \jvhlch 1s least Shghtly smaller than that of Saldsecond bore, integral with sand head and the u er cf l S an expandingsection of a diameter slightly greater f f wh 1s substantlally parallelWlth the than that of said first bore, there being a shoulder jacentinner surface of said groove, said sleeve havat the junctions of saidpulling and expanding secing a Continuous axial passageway extendingthefetions and a locking groove adjacent thereto but through comprisedof a cylindrical bor g n spaced toward said pulling section, and a blindhead dameer 1g snd shtankand a; idwnlilf co g e e of ad diametersllghtly dgreater tgan that of sailgl ex- 0 re 6 19-1116 6f lll'sal eaere 6mg an pan ing section, sai expan ing section eing annular opghbbulder in said passageway at the adapted upon an axial pulling forcebeing applied jun ti n 0 Sal Ores; to said pulling section and areactive force being anda pin including an expanding section of adiameter constantly applied to said locking crown to be pulled shghfiygreatter than that ofdthef borle 1n saldd Sha k, itto said (sihank toexpand tliie same aliidhto wiredraw a pn ing sec mm on one en 0 Sal epan g 86 own in iameter in accor ance wit t e resistance tion of adiameter smaller than that of the latter secof expansion of said shank,and said blind head hetion andadapted to be initially disposed withinsaid ing adapted upon the continued application of such Siefive Wlth aPP P-Z end thereof p l q g from 40 forces to be pulled into said shankto further expand the 1:212:33 epnrdJ jgitsglg fsrlgget 122d fillflli St; g f f d thedszirlneatlie egtent to Hugh said expianclllingkseztion 1g 1 1 s 1 611 31 an In ea are pu e into sai s an eing Sleeve, 9 a iheadpn the pp end of Said limited by the shoulder on said pin at thejunction Z5t 1 nZiiZeifio n iifi iiifig i 11132? if a at jfi fiexpandini swim engaging Said a stop s on er, w ereupon t e applicationof such the luncltlonl ofksaldopunmg, q P g forces causes said lockingcrown to be buckled into annu ar 06 mg atom/6.111 mg Sectlon "i thelocking groove of said pin with said locking acent the shoulder at theunction of the latter with crown closing said recessed annular groove,followed said expanding section and an annular breakneck b slid-n of 0 1f f 1 oove in said pulling section at a location adjacent y 1 01 6 mca 9Sal 00 ii to and longitudinally spaced from said locking crown We aongcomqa surfilce of Sal groove toward the gripping end of Said pullingrecessed annular groove, into said locking groove tion, said expandingsection and blind head being of Sald adapted successively upon a pullingforce being applied to said pulling section and a reactive forceReferences Cited by the Exammer being applied to said crown to move intosaid shank UNITED STATES TENT to expand the same until the leading edgeportion 2 298 203 10/1942 Ekhmd 85 72 of the shoulder at the junction Ofsaid pulling and Huck expanding sections engages the stop shoulder insaid 2501567 3/1950 Huck 8578 tubular sleeve to sharply increase theresistance to 2 526 235 10/1950 H k 85 7 pin movement, whereupon thecontinued application 2931532 4/1960 uc 8 of such forces results in thesaid locking rown b Gapp 8578 ing buckled into the locking groove insaid pin and FOREIGN PATENTS flattened into the annular groove in saidsleeve head and, thereafter, in said pin fracturing at said break-1,254,584 1/1961 France' CARL W. TOMLIN, Primary Examiner.

7. The subject matter of claim 6, further characterized in that thevolume of the portion of said locking crown projecting outwardly of saidsleeve head is approximate- EDWARD C. ALLEN, Examiner.

M. PARSONS, JR., Assistant Examiner.

1. A BLIND RIVET ADAPTED TO BE INSERTED FROM THE TOP SIDE AND SET IN THEALIGNED APERTURES IN A PLURALITY OF WORK PIECES, COMPRISING: A TUBULARSLEEVE INCLUDING A SHANK WITH A RADIALLY ENLARGED HEAD AT ONE END AND ANAXIAL PASSAGEWAY EXTENDING THERETHROUGH FROM END TO END, SAID SLEEVEBEING ADAPTED TO BE INSERTED INTO THE ALINGED APERTURES IN THE WORKPIECES WITH SAID HEAD ABUTTING THE TOP SIDE OF THE SAME AND WITH THESHANK PROJECTING FROM THE OPPOSITE BLIND SIDE OF THE WORK PIECES; A PININCLUDING, IN SERIES, A PULLING SECTION INITIALLY DISPOSED IN SAIDPASSAGEWAY WITH A GRIPPING END PROJECTING FROM THE HEADED END OF SAIDSLEEVE, AND EXPANDING SECTION OF A CROSS-SECTION GREATER THAN THAT OFSAID PASSAGEWAY AND INITIALLY PROJECTING FROM THE SHANK END OF THESLEEVE, AND A BLIND HEAD OUTWARD OF, AND LARGER IN DIAMETER THAN SAIDEXPANDING SECTION SO AS TO PROVIDE AN ANNULAR TAPERED SECND SHOULDER ATTHE JUNCTURE OF THE BLIND HEAD AND EXPANDING SECTION, SAID EXPANDINGSECTION BEING ADAPTED UPON AN AXIAL PULLING FORCE BEING APPLIED TO SAIDPULLING SECTION AND A REACTIVE FORCE OPPOSITE TO SAID RADIALLY ENLARGEDHEAD TO BE DRAWN INTO SAID PASSAGEWAY TO EXPAND THE PROJECTING PORTIONOF SAID SHANK AND, THEREAFTER, THE PORTION THEREOF DISPOSED WITHIN THEALIGNED APERTURES IN SAID WORK PIECES, SAID BLIND HEAD BEING ADAPTEDUPON THE CONTINUED APPLICATION OF SUCH THAT OF AT LEAST SAID EXPANDINGSECTION AND SAID SECSHANK TO FURTHER EXPAND THE SAME; FIRST SHOULDERMEANS ON THE EXTERIOR OF SAID PIN AXIALLY SPACED FROM SAID SECONDSHOULDER TOWARD SAID PULLING SECTION, WHICH IS OF A UNIT HARDNESSGREATER THAN THAT OF AT LEAST SAID EXPANDING SECTION AND SAID SECONDSHOULDER, AND STOP SHOULDER ON THE INTERIOR OF SAID SLEEVE ADJACENT SAIDRADIALLY ENLARGED HEAD ENGAGEABLE TO STOP PIN MOVEMENT, SAID EXPANDINGSECTION BEING ADAPTED TO BE PULLED INTO THE BLIND END OF SAID SHANK TOEXPAND THE SAME AND TO WIREDRAW DOWN IN DIAMETER AND, THEREAFTER, SAIDBLIND HEAD BEING ADAPTED TO BE PULLED INTO SAID SHANK TO FURTHER EXPANDTHE SAME WITH SAID SECOND SHOULDER BEING DRAWN UP ADJACENT THE BLINDSIDE OF THE WORK PIECES AND DEFORMED TO EXPAND THE AXIALLY ALIGNEDPORTION OF THE SHANK INTO ENGAGEMENT WITH THE BLIND SIDE OF THE WORKPIECES, THE EXTENT TO WHICH SAID EXPANDING SECTION AND BLIND HEAD AREPULLED INTO SAID SHANK AND SAID SECOND SHOULDER IS DEFORMED BEINGLIMITED BY THE LEADING EDGE OF SAID FIRST SHOULDER ABUTTING SAID STOPSHOULDER IN SAID SLEEVE; AND MEANS ADJACENT SAID RADIALLY ENGLARGED HEADFOR LOCKING SAID PIN AGAINST MOVEMENT RELATIVE TO SAID SLEEVE, AND MEANSLOCATED ON SAID PIN ADJACENT SAID FIRST SHOULDER AND BETWEEN SAID FIRSTSHOULDER AND SAID PULLING SECTION FOR RECEIVING SAID LOCKING MEANS.